Headbox with bottom wall having controllable deflection



April 1967 L. E. DENNIS ETAL 3,313,681

HEADBOX WITH BOTTOM WALL HAVING CONTROLLABLE DEFLECTION Filed Aug. 27,1964 5 Sheets-Sheet 1 1 N VEN TORS 100/6 6 7013:

A ril 11, 1967 L. E. DENNIS ETAL 3,

HEADBOX WITH BOTTOM WALL HAVING CONTROLLABLE DEFLECTION Filed Aug. 27,1964 5 Sheets-Sheet 2 d a I, 44/ C7 o fcx fe m M ATTORNEYS April 1967 L.E. DENNiS ETAL 3,333,681

HEADBOX WITH BOTTOM WALL HAVING CONTROLLABLE DEF'LECTION Filed Aug. 27,1964 5 Sheecs-Sheet 5 Era 5 INVENTOR.

4 //1/ C mkwzfl a 1% v ATTORNEYS April 1967 L. E. DENNIS ETAL 3,313,681

HEADBOX WITH BOTTOM WALL HAVING CONTROLLABLE DEFLECTION Filed Aug. 27,1964 5 Sheets-Sheet 4 INVENTOR. 100/6 M67705 [0.0/6 f @f/V/V/S April 11,1957 L. E. DENNIS ETAL 3,313,681

HEADBOX WITH BOTTOM WALL HAVING CONTROLLABLE DEFLECTION Filed Aug. 27,1964 5 Sheets-Sheet 5 1 N VEN TOR. ZOO/6 fl Z 6%0555 44 //1/ C @OKCM?[WW/Mam kzdy ,44- ATTORNEYS United States Patent 3,313,681 IEADBOX WITHBOTTOM WALL HAVING CONTROLLABLE DEFLECTION Louis E. Dennis, Clinton, andLouis M. Stuebe and Alvin C. Roecirer, Beioit, Wis., assignors to BeloitCorporation, Beloit, Wis., a corporation of Wisconsin Fiied Aug. 27,1964, Ser. No. 392,460 10 Claims. (Cl. 162252) The present inventionrelates to improvements in paper machine headboxes and more particularlyto a headbox having an improved apron board and support structuretherefor.

In a paper machine headbox the apron board is positioned in the floor ofthe box ahead of the slice opening through which the paper stock slurryis discharged onto a traveling forming surface. At the edge of the apronboard is mounted an apron lip which forms the lower edge of the sliceopening. If deflections in the apron board occur due to the weight ofthe stock in the headbox and due to pressures in a closed headbox, theapron board and apron lip will deflect downwardly in the center toresult in a non-uniform slice opening. This can be taken care of byadjustment of the upper slice lip but it is also important that the edgeof the apron lip be parallel to the forming surface. In a Fourdriniermachine it is desirable to design the apron board to match breast rolldeflection. The stock should be discharged on the Fourdrinier wire at anoptimum location just in advance of the forming board (if a formingboard is 1 used) and any differences in deflection between the apronboard and the breast roll will cause the stock to be distributed in anon-uniform lateral line across the Fourdrinier wire. Deflection of thebreast roll can change with the load including stock pressure, rollweight and wire tension, and deflection control means can be used insome instances to control deflection of the breast roll.

In pressure headboxes and high speed papermaking machines substantialforces occur on the apron board and these forces will change with changein headbox pressures. As the speed of the machine is increased and thespeed of travel of the forming wire increases, the headbox pressure isincreased as a function of the square of the speed. In addition tochanging headbox pressure, papermaking runs involve changingtemperatures of the stock. This will change the temperature of thesurface of the apron board within the headbox without necessarilychanging the temperature of portions of the apron board supportstructure remote from the surface of the apron board exposed to the box,and thermal deflection will change the position of the apron board.

Headbox design practice conventionally attempts to compensate forvarious factors which would cause apron board distortion by making theapron board support heavy and deep to minimize mechanical and thermaldeflection in operation. This of course involves expensive constructionparticularly with machines which are very wide. Such construction isexpensive in the requirements of structural members and in shipping andsetting up costs. It is also current practice to attempt to design theapron board to match breast roll deflection. Thi is usually done at anoptimum or given Fourdrinier wire speed and corresponding pressure inthe headbox. However, with changing operating conditions the designfactors are no longer satisfactory. For example, the customer may changewire tension thereby changing breast roll deflection and causing anunmatch of deflections in the breast roll and apron lip. Obviously,changes in headbox pressure and changes in stock temperature will causea different distortion of the apron board and hence a mismatch in thecurvature of the apron lip and breast roll. An object of the presentinvention is to provide an improved headbox structure wherein it isunnecessary to provide expensive over-designed apron board supportswhich have heretofore been necessary to minimize mechanical and thermaldeflection of the apron board and apron board lip during operation.

A further object of the invention is to provide an improved apron boardconstruction wherein mismatch in the curvature of the breast roll andapron board lip is avoided and wherein changes in curvature of thebreast roll can be compensated for by actually changing the curvature ofthe apron board lip and wherein changes in headbox pressures and changesin headbox temperatures need not cause changes in apron boarddeflection.

A further object of the invention is to provide an improved headboxstructure having an apron board wherein the apron board lip can beadjusted in its height during operation so that the stock will dischargeupon the traveling Fourdrinier wire at an optimum location to therebyimprove formation of the paper web and to avoid the disadvantages in badformation which occur with non-uniform discharge across the machine orwith discharge at an improper location relative to the breast roll andforming board.

A general object of the invention is to provide an improved headboxdesign which will provide an improved quality of paper and improve theuniformity of the paper across the width of the Fourdrinier by making itpossible to accurately match the apron board deflection with the breastroll deflection and by making it possible to easily adjust the apronboard lip to the optimum height and accommodate changes in operatingfactors such as headbox pressure and temperature.

A feature of the present invention provides a headbox with an apronboard designed to be incapable in itself of supporting the forces fromthe stock within the headbox and wherein a controllable adjustable forceapplying means is applied along the width of the apron board to controlits deflection. Preferably this deflection control force is in the formof a fluid chamber wherein a uniform upward fluid pressure is appliedbeneath the apron board with the pressure being variable to accommodatechanges in headbox pressure or temperature. The apron board is securedat its ends and the upwardly directed fluid chamber pressure will changethe deflection or curvature of the apron board along its length. In oneform, the apron board is in eifect a floating member being hingedlyattached at its rear edge and having flexible seals at its edge andbeing adjustably secured at its ends for controlling the elevation ofthe apron lip and for obtaining controlled curvature.

Other objects, advantages and features will become more apparent withthe teaching of the principles of the present invention in connectionwith the disclosure of the preferred embodiments thereof in thespecification, claims and drawings, in which:

FIGURE 1 is a somewhat schematic side elevational view of a pressureheadbox constructed and operating in accordance with the principles ofthe present invention;

FIGURE 2 is a fragmentary vertical sectional view taken substantiallyaloong line II-II of FIGURE 1;

FIGURE 3 is a schematic side elevational view shown in section, of aheadbox of a modified form and constructed and operating in accordancewith the principles of the present invention;

FIGURE 4 is a schematic vertical sectional view taken substantiallyalong line IV-IV of FIGURE 3;

FIGURE 5 is a sectional view similar to FIGURE 4 but showing anotherform of the invention;

FIGURE 5a is a fragmentary schematic view showing an arrangement forcontrolling deflection of the apron board;

FIGURE 6 is a vertical sectional view taken through a headbox showinganother form of the invention;

FIGURE 7 is a side elevational view taken through a headbox showing afurther form of the invention;

FIGURE 8 is a side elevation view of a headbox of substantially theconstruction of the arrangement of FIG- URES 3 and 4 and showing thelocation of a stop arrangement; and

FIGURE 9 is a diagrammatic view of a control for the pressurearrangement for supporting the apron board.

On the drawings:

FIGURES l and 2 show a headbox structure incorporating a pressureheadbox 10 for discharging paper stock slurry onto a traveling formingsurface provided by a Fourdrinier wire 12 supported on a breast roll 11.

The stock is supplied to the headbox it) through pipes or tubes 13 andthe stock flows through an upwardly inclined passage portion 14 and avertical passage portion 15 into the headbox chamber 16 which has theusual rectifier rolls such as 24. Stock in the headbox is maintainedunder a predetermined pressure and is emitted from a slice Opening 17,the size of which is controlled by an upper slice lip 18.

The headbox floor is defined in advance of the slice opening by theupper surface 19 of an apron board 21. At the front edge of the apronboard 21 is a lower slice lip or apron lip 20 which defines the loweredge of the slice opening 17. As above discussed, the breast roll 11will tend to deflect or sag downwardly at its center and the sliceopening 11 should have a contour parallel to the breast roll so that thestock is discharged at the same location, relative to the breast rolland to a forming board which may follow the breast roll, completelyacross the machine. This requires that the apron board 21 have acurvature or deflection so that the apron lip 20 is parallel to thebreast roll 11. For optimum web formation, the apron lip 20 should bethe proper height above the wire to discharge the stock for engagementwith the wire at the optimum location which should be just in advance ofthe forming board. With change in headbox pressures it will be apparentthat the trajectory of the stock will change so that it is desirablethat the vertical location of the apron lip 20 be changed. The sliceopening should be controlled solely by adjustment of the vertical upperslice lip 18 and the lower apron lip be positioned at the optimumelevation and optimum curvature. These features are made possible forvarying operating conditions by controlling the deflection of the apronboard 21.

The apron board is fabricated to be of a convenient size but need not beover-designed and can be of relatively light weight so as to bedeflectable and incapable in itself of resisting the downward forcesexerted from the pressure of the stock within the box. Positioned belowthe apron board 21 is a lower support member 22. Between the supportmember and the apron board is a fluid pressure chamber illustrated inthe form of rubber bladders 23.

As illustrated in FIGURE 2 the rubber bladders 23 each are provided withinflation openings 25 to which a line is attached containing acontrolled air pressure for controlling the pressure within the bladderswhich are preferably maintained at the same pressure and a convenientnumber of bladders is chosen in accordance with commercially availablebladder structures. However, if the deflection of the breast roll isnon-uniform or breast roll anti-deflection means are provided which donot obtain a uniform sag of the roll the bladders may be nonuniformlypressurized to obtain a deflection of the apron board to conform to thedeflection of the breast roll.

In the arrangement of FIGURES 1 and 2, the ends of the apron board 21are rigidly supported such as by being carried in the upper ends ofcolumns 26 and 27. These columns conveniently provide seats 30 and 31for the ends of the lower support member 22 and shims may be inserted atthe base of the seats to obtain a convenient height for the supportmember 22. In other forms, the support member 22 may rest on the flooror the floor itself may be used as the support member.

Shims 28 and 29 are similarly provided at the upper ends of the columnto establish the height of the apron board 21. This will determine thelocation of the ends of the apron lip 2% corresponding to the fixedlocation of the ends of the breast roll 11. The deflection of the centerof the apron board and of the apron lip 20 is determined by the airpressure within the air bags 23. Mill air pressure is used for a sourceand conventional pressure control valves are used for maintaining apredetermined pressure in the bags 23. The pressure is determined as afunction of the pressure within the headbox and/ or a function of thetemperature of the stock as will be further described in connection withFIGURE 9.

In the arrangement of FIGURES 3 and 4 a free floating apron board isemployed pivotally hinged at its back edge to the headbox. A headbox 35is provided with a suitable pressure stock supply such as from a fanpump with the pressure being controlled by suitable manual or automaticcontrol mechanism. The headbox is enclosed by a rear wall 52, a topcover 52a and a front slice 38 with connected sides 50 and 51. The inletpassage into the headbox has a back wali and rear floor 39 and the stockflows through the headbox to be ejected from a slice opening 37. Withinthe box the floor is provided by an upper surface 41 of an apron board40. At the front edge the apron board carries an apron lip 42 and abridging plate 43 secured along one edge to the apron board 40 and alongthe other edge to the headbox wall 39 forms a pivot support for theapron board.

The apron board is sealed at its sides by sliding seals 48 and 49 whichprevent the paper stock from within the headbox chamber from passingdown into the pressure chamber 44- beneath the apron board 4% andprevent the fluid in the pressure chamber from passing upwardly into thestock. Operation is contemplated in the form shown by permitting freefloating movement of the apron board 40 supported solely by a hinge 43at its rear edg by end supports which determine the elevation of theends of the apron lip, and by the pressure of the fluid within thepressure chamber 44 beneath the apron board. The side edges of the apronboard 40 are anchored at a predetermined location, which may beadjustable and the pressure chamber determines the deflection of theapron board and provides the primary vertical support therefor. As willbe noted, the apron board can be formed of a relatively lightconstruction incapable in itself of resisting the forces from thepressure of the stock in the box with the pressures being carried by thefluid in the pressure chamber 44 beneath the apron board. This permits asaving in construction costs for the apron board since its deflectionproperties are not critical. The pressure chamber is closed at its lowersurface by support member 45 which is of adequate strength to supportthe apron board but need not be of critical deflection properties. Thelower support 45 may be carried from the floor by being supported on endcolumns such as shown at 46.

End support means are provided to determine the position of the ends ofapron board and of the apron lip 42. These also act as stops to preventdamage to the machine in the event of loss of pressure within theheadbox such as accidental stopping of the fan pump. They also preventdamage to the wire in the event of loss of pressure in the pressurechamber 44 or upon shut-down of the machine with the apron board 40moving to its lowermost position.

The end support means are provided by end rods 50 and 51 secured to theapron board ends preferably near the front thereof, and passing downthrough the lower support member 45. The support member is provided withsuitable openings with seals such as 5911 and 51a. At the lower end ofthe rods are stop nuts such as 52 and 53 which engage a stop bracket 54and thread up or down against the bracket. The nuts are shown spacedfrom the bracket but in operation at least the upper or lower nut willengage the bracket so that a bending force is applied to the apronboard.

In order to indicate the position of the apron board indicators 55 and56 are provided. A plurality of indicators may be provided .along thelength of the apron board to show a deflection or bending. Ordinaryvisual indicators may be provided as illustrated schematically in thedrawings, or other automatic indicators may be provided to supply anoutput return signal where an automatic pressure control mechanism isused to control the pressure in the pressure chamber as a function ofvarious machine operating factors. The fluid in the chamber may be airor other suitable hydraulic medium or the stock itself may be used for apressure fluid in the chamber 44.

FIGURE 5 shows a headbox 60 with a chamber therein. In this structure apressure headbox may be employed or an atmospheric pressure box can beemployed and each are subjected to changing forces on the apron boardfrom the stop although the range of variation with the pressure headboxis obviously greater.

The floor of the headbox 60 in advance of the slice opening is providedby an apron board 62 and inasmuch as the side appearance of thestructure of the headbox will be apparent from the previous descriptionsan elevational view will suflice for the arrangement of FIG- URE 5.Below the apron board is a fluid pressure chamber 65 with the fluidexposed on its upper surface to the apron board. Suitable upper andlower seals 63 and 64 are provided between the side walls of the headboxand the side edges of the apron board. The pressure chamber 65 isdefined along its lower surface by a support member 66.

At the edges of the apron board 62 are laterally extending projectionswhich protrude through openings in the headbox side walls and areprovided for determining the elevation of the sides of the apron board62. Attached to the projections 67 and 68 are vertical adjusting means69 and 71). Various suitable adjusting means may be employed which setthe location of the ends of the apron board 62 and an upper threaded rod71 is secured to a lug 78 on the side of the headbox and a lowerthreaded rod 72 is secured to the projection 68. An adjustmentturnbuckle 73 connects to the rods which are threaded in oppositedirections and rotation of the turnbuckle at each end will determine theposition of ends of the apron board. This position is adjusted topositively locate the elevation of the slice lip relative to the breastroll.

FIGURE 5a illustrates an arrangement wherein deflection of the apronboard is determined by anti-deflection means employing a deflectingforce couple applied at each end of the apron board. Only one edge ofthe apron board need be shown since both edges are similarly provided.

An apron board 74 is shown with a projection 75 extending rigidlytherefrom through an opening in a side wall of a headbox. A force coupleis applied to the projection such as that including an upward force 76applied close to the headbox and a downward force 77 applied spacedoutwardly from the upward force 76. Suitable force applying means suchas inflatable bellows may be used and extension 75 is rigidly secured tothe end of the board. As will be recognized this arrangement may be usedfor determining the elevation of the ends of the apron board as well asfor applying a deflection force. This deflection force may be utilizedin combination with pressure in a chamber of fluid beneath the apronboard or without such a chamber. Also, the chamber may be employedmerely to support the force of the stock in the headbox and control ofdeflection obtained wholly by the force couples applied at the ends ofthe apron board.

In the arrangement of FIGURE 6, a headbox 88 has a front verticallymovable slice lip shown schematically at 82 with a slice opening 81.Stock flows into the headbox through passages 83 at the rear of theheadbox and up over a rigid rear wall 84. The floor of the headbox inadvance of the slice opening 81 is provided by an apron board 85 havinga hinge member 86 at its rear edge. The hinge member is cylindrical inshape fitting into a cylindrical socket 87 provided at the upper edge ofthe wall 84. A pressure chamber 88 is provided being wholly beneath theapron board 85 and confined by lateral flexible seals 91 and 92. Thepressure chamber has a lower support member 89 beneath it and anadjustable stop means 90 may be employed.

In FIGURE 7, :a headbox is provided with an adjustable slice lip 97 anda slice opening 98 Therein. The stock is received through an inletpassage means 96. In this structure the apron board is combined with therear wall to provide an apron assembly 99 hinged at the base of the rearwall on a hinge member 100 which is cylindrical in shape and fits into ahinge socket 101. In this arrangement, as the elevation of the floor ofthe headbox is changed, the width of the throat forming part of theinlet passage 96 is also changed. For supporting the apron boardassembly 99 a fluid pressure chamber 102 is provided having an exposedsurface engaging horizontal and vertical surfaces of the apron board. Alower support member 103 provides the support for the fluid in thechamber and flexible seals 104 and 105 extend between the support member103 and the apron board assembly 99 In the arrangement of FIGURE 8 anadjustable stop is provided to limit the lower pivotal movement of theapron board and a headbox has an adjustable vertical slice lip 112controlling a slice opening 113. An apron board 114 is supported on ahinge plate 117 at its rear edge and a chamber filled with pressurizedfluid extends beneath the apron board. In each of the fluid pressurechambers illustrated it will of course be understood that suitable inletand outlet Openings are provided and these are omitted for the sake ofclarity of the drawings.

Beneath the chamber 115 is a support member 119 through which individualor a plurality of stop screws 118 are threaded. The upper ends of thesestop screws are engaged by the apron board 114 in its lowermost positionto prevent the apron lip 120 from engaging and damaging the wire andbreast roll.

FIGURE 9 illustrates a pressure control system for the pressure chambersbeneath the apron board. A control pressure signal indicative ofpressure within the headbox is received through a line 125. A controlpressure signal indicative of pressure of the stock is received througha line 126. These are fed into a proportional control 127 which iscalibrated to control the pressure in a pressure chamber 128 forobtaining the proper support and proper deflection of the apron board inaccordance with the factors of pressure and temperature. The temperaturesignal largely compensates for change in deflection due to increase ordecrease of the temperature of the upper surface of the apron boardwhich heretofore could not be controlled when the temperature of thepaper stock slurry changed.

The proportional control supplies a signal to a valve mechanism 131which controls a fluid pressure supply' 130. A feed-back signal isreceived from the chamber 128 through a line 129, and supplied to theproportional control. For obtaining a controlled pressure within thechamber 128 a return recirculation line 133 is provided with controlledbleed valves 134. As will be observed while the present arrangementregulates the flow of fluid into the chamber other arrangements may beemployed such as wherein a uniform flow is supplied and the opening ofreturn bleed valves is regulated by a control valve mechanism such as131.

In operation, with reference to the arrangement of FIGURES 1 and 2, theelevation of the apron lip 20 above the breast roll is determined bysetting the height of the ends of the apron board 21 such as byinserting shims 28 and 29 of the proper height. Mechanism which can bemore easily adjusted during operation can also be employed. To supportthe forces on the apron board 21 from the stock within the headbox theinflatable bags 23 are inflated to a pressure which is determined as afunction of headbox pressure and/or stock temperature and this pressureis modified to obtain a predetermined deflection of the apron board sothat the apron lip will follow the exact deflection of the breast roll.With changes in breast roll deflection due to factors extraneous of theheadbox, such as change in tension of the Fourdrinier wire, an externalsignal may be fed to the mechanism for controlling the pressure in thebags 23. With change in operating factors which require a change inelevation of the slice lip over its overall length relative to thebreast roll and wire, such as a change in headbox pressure toaccommodate change in speed of the wire, the elevation of the ends ofthe apron board are changed along with a change in pressure in the fluidpressure chamber beneath the apron board to thereby effect a change inelevation of the apron board without necessarily a change in deflection.Changes in deflection are obtained by a change in pressure in thepressure chamber without changing the location of the position at whichthe apron board ends are locked. Increase in temperature of the stockcauses increasing deflection upwardly in the center of the apron boardand is compensated by a reduction in the fluid pressure beneath theboard. Increased or decreased headbox pressure is compensated for bycorresponding increased or decreased chamber pressure.

Thus, it will be seen that we have provided a device which meets theobjectives and advantages above set forth and obtains proper apron lipcurvature with speed change and pressure change. The device effectsadvantages in economics in that a simple pressure chamber is used notonly to control deflection of the apron board but also to sustain theforces of the pressures within the box so that the apron board no longerhas to be designed deep and strong and now can be designed only formaximum stress and no longer need be designed for deflection. The deviceobtains a control over formation of the stock and it permits changingelevation of the apron lip with the characteristics of flow onto thewire and permits changing the location where the stock hits the wire.This avoids the formation of bubbles which occur if the stock hits toofar forwardly relative to the breast roll and avoids stapling onto thewire if the stock hits too far back and permits the trajectory changeswhich occur as headbox pressures change, which must be provided for withwire speed change.

It is contemplated that other means may be provided for exerting forceon the apron board such as individual diaphragms, levers, jacks, cams orwedges which are interposed between the apron board and the lowersupport members. These of course will not normally accomplish the upwardchange in force as uniformly as a continuous fluid chamber. Theinvention permits the operator for the first time to determine the truedeflection of the apron board and control it to obtain optimumoperational conditions.

The drawings and specification present a detailed disclosure of thepreferred embodiments of the invention, and it is to be understood thatthe invention is not limited to the specific forms disclosed, but coversall modifications, changes and alternative constructions and methodsfalling within the scope of the principles taught by the invention.

We claim as our invention:

1. In a papermaking machine the combination comprising,

a closed pressure headbox having an inlet for receiving a flow of paperstock and having a slice opening for 8 discharging the stock onto atraveling forming surface,

means for delivering stock under pressure to the headbox inlet,

an apron board in the headbox in advance of the slice opening incapablein itself of supporting the internal forces from the stock pressure inthe headbox,

pressure signal means for providing a signal corresponding to thepressure of stock in the headbox,

and force applying means applying a force to the apron board and beingcontrollably connected to the signal means deflecting the board upwardlya predetermined amount as a function of the pressure in the headbox.

2. In a papermalring machine the combination comprising,

a headbox having an inlet for receiving a paper stock slurry and havinga slice opening for discharging stock onto a traveling forming surface,

an apron board in said headbox in advance of the slice opening incapablein itself of withstanding the forces of the stock within the headbox,

means measuring the temperature of the stock within the headbox fordetecting the temperature of the surface of the apron board Within theheadbox and providing a temperature signal,

and force applying means in force transmitting relation to said apronboard for applying a deflecting force to the board counteracting forcesof the stock within the headbox for obtaining a deflection of the boardin a predetermined amount as a function of stock temperature.

3. In a papermaking machine the combination comprising,

a headbox having an inlet for receiving a flow of paper stock and havinga slice opening for discharging the stock on a traveling formingsurface,

an apron board in advance of the slice being incapable in itself ofsupporting the force of the stock,

fluid pressure means in force transmitting relation to the board forapplying an upward supporting force to the board,

said fluid pressure means having a lower wall supported independently ofthe headbox,

and positive stop means for limiting the movement of the board in avertical direction.

4. In a papermaking machine the combination comprisa headbox having aninlet for receiving a flow of paper stock and having a slice opening fordischarging the stock on a traveling forming surface,

an apron board in the headbox in advance of the slice opening,

and means connected at each end of said apron board for applying acontrollable force couple in a direction counteracting the downwardforce of the fluid within the box and bending the board upwardly againstthe deflection forces of the stock within the box.

5. In a papermaking machine the combination comprisa headbox having aninlet for receiving a flow of paper stock and having a slice opening fordischarging the stock on a traveling forming surface,

an apron board means positioned ahead of the slice opening having anupper horizontal surface forming the floor of the headbox and a leadingvertical surface ahead of the horizontal surface forming a portion of apassage leading into the headbox,

hinge means for the board means at the top of said vertical surfacehingedly connecting the board means to the headbox,

means defining a fluid pressure chamber having a vertical portion belowsaid hinge means and a horizontal portion with the fluid exertinghorizontal and vertical forces on the board means toward the directionof said surfaces against the pressure of stock in the headbox,

seals for the chamber permitting pivotal movement of the board,

said pressure chamber having a lower wall supported independently of theheadboX,

and means for deliverin fluid to the chamber controlling the pressuretherein.

6. In a papermaking machine the combination comprising,

a headbox having an inlet for receiving a flow of paper stock and havinga slice opening for discharging the stock on a traveling formingsurface,

an apron board in the headbox in advance of the slice opening,

means pivotally attaching said board along its rear edge to the headbox,

and means defining a fluid pressure chamber beneath the apron board withthe fluid in the chamber for applying an upward supporting force to theboard,

means delivering fluid to the chamber for controlling the pressuretherein,

and an adjustable fixed stop projecting into the chamber engageable bythe board for limiting downward movement thereof.

7. In a papermaking machine the combination comprisa closed pressureheadbox having an inlet for receiving a flow of paper stock and having aslice opening for discharging the stock onto a traveling formingsurface,

means for delivering stock under pressure to the headbox inlet,

an apron board in the headbox in advance of the slice opening incapablein itself of supporting the internal forces from the stock pressure inthe headbox,

pressure signal means providing a signal corresponding to the pressureof stock in the headbox,

means measuring the temperature of the stock within the headbox fordetecting the temperature of the surface of the apron board within theheadbox and providing a signal corresponding to stock temperature,

and force applying means for applying a force to the apron board andconnected to receive said temperature signal and said pressure signalfor deflecting the board upwardly a predetermined amount as a combinedfunction of the temperature and pressure in the headboX.

8. In a papermaking machine the combination comprisa headbox having aninlet for receiving a flow of paper stock and having a slice opening fordischarging the stock on a traveling forming surface,

a bottom wall in the headbox in advance of the slice opening facing theentire pond of the stock in the headbox and incapable in itself ofsupporting the internal forces from the stock,

means defining a fluid pressure chamber having an upper movable wall inforce transmitting relation with the bottom wall and extendingcompletely across the headbox,

a lower wall for the chamber supported independently of the headboX, and

fluid delivery means connected to the chamber for controlling thepressure therein to control the vertical uniform force applied acrossthe entire surface of said headbox bottom Wall.

9. In a papermaking machine the combination comprisa headbox having aninlet for receiving a flow of paper stock and having a slice opening fordischarging the stock on a traveling forming surface,

a bottom wall having an upper surface located in the headbox ahead ofthe slice opening and being freely vertically movable relative to saidheadbox,

fluid seals at the lateral side edges of the bottom wall between saidwall and headbox permitting relative sliding movement therebetweeneliminating bending stresses with change in vertical position of thebottom wall,

means defining a closed fiuid chamber beneath the full width of thebottom wall with the wall supported on the upper surface of fluid in thechamber,

said chamber having a lower wall supported independently of the headbox,

and fluid supply means controlling the pressure of the fluid in thechamber so that the location of the upper surface of the headbox bottomwall may be controlled with change of forces on the headbox bottom wallfrom stock within the headbox.

10. In a papermaking machine the combination comprising,

a headbox having an inlet for receiving a flow of paper stock and havinga slice opening for discharging the stock on a traveling formingsurface,

an apron board in the headbox in advance of the slice opening,

means pivotally attaching said bottom wall along its rear edge to theheadbox,

a support member beneath said bottom wall supported independently of theheadboX,

means defining a fluid pressure chamber beneath the bottom wall andsupported on the support member with the fluid in the chamber supportingsaid bottom wall, and flexible seals at the forward and rear edge and atthe ends between said support member and said bottom wall.

References Cited by the Examiner UNITED STATES PATENTS 1,028,573 6/1912Kutter l62336 1,240,589 9/1917 Murray 162353 X 1,579,204 4/1926 Berry162-353 X 2,241,688 5/1941 Williams 162341 2,779,253 1/1957 Owens 1623442,928,464 3/1960 Western et a1 162347 S. LEON BASHORE, Acting PrimaryExaminer.

DONALL H. SYLVESTER, J. H. NEWSOME,

Assistant Examiners.

1. IN A PAPERMAKING MACHINE THE COMBINATION COMPRISING, A CLOSINGPRESSURE HEADBOX HAVING AN INLET FOR RECEIVING A FLOW OF PAPER STOCK ANDHAVING A SLICE OPENING FOR DISCHARGING THE STOCK ONTO A TRAVELINGFORMING SURFACE, MEANS FOR DELIVERING STOCK UNDER PRESSURE TO THEHEADBOX INLET, AN APRON BOARD IN THE HEADBOX IN ADVANCE OF THE SLICEOPENING INCAPABLE IN ITSELF OF SUPPORTING THE INTERNAL FORCES FROM THESTOCK PRESSURE IN THE HEADBOX, PRESSURE SIGNAL MEANS FOR PROVIDING ASIGNAL CORRESPONDING TO THE PRESSURE OF STOCK IN THE HEADBOX, AND FORCEAPPLYING MEANS APPLYING A FORCE TO THE APRON BOARD AND BEINGCONTROLLABLY CONNECTED TO THE SIGNAL MEANS DEFLECTING THE BOARD UPWARDLYA PREDETERMINED AMOUNT AS A FUNCTION OF THE PRESSURE IN THE HEADBOX.